Basically I am thinking of a series of independent steps. You run one program to start off the process. This program gets an updated set of questions from some public url. The overall scope of what needs to be installed is determined by this step. For instance, if you already have daemontools installed, you should be able to skip that installation step. This initial program would write the answers down for later re-use or re-distribution, and use the answers as input to the next step.
The second step would be to query the public url for specific knowledge on each sub-installation step. This would probably include an additional series of questions specific to each piece of software that needs installation. Again, these answers would be saved into a re-useable re-distributable file. Certain of these questions would probably need flagging as private and/or instance dependent so that partial re-use could be possible.
The third step would acquire the necessary software, archive it, run installation and configuration scripts, record and archive the output of all this process, and maybe test installation and record the results. It should also be possible to step through the installation one command at a time.
Whatever this wizard turns out to be, it should be easy for someone to add new parts, or re-use the wizard on their own private url. The only real requirements here should be that the software should be able to be installed via a series of shell commands, and the software is accessible to the wizard via a public or private url. It might be convenient to have some type of interactive tool that could record your steps, and allow you to explain each step as you proceed. The hardest part will be the writing of configuration files, because this is usually not done via a command line, however this is also the hardest part to document correctly.